// Copyright (c) 2021, gottingen group.
// All rights reserved.
// Created by liyinbin lijippy@163.com
//
// -----------------------------------------------------------------------------
// File: node_hash_map.h
// -----------------------------------------------------------------------------
//
// An `abel::node_hash_map<K, V>` is an unordered associative container of
// unique keys and associated values designed to be a more efficient replacement
// for `std::unordered_map`. Like `unordered_map`, search, insertion, and
// deletion of map elements can be done as an `O(1)` operation. However,
// `node_hash_map` (and other unordered associative containers known as the
// collection of abel "Swiss tables") contain other optimizations that result
// in both memory and computation advantages.
//
// In most cases, your default choice for a hash map should be a map of type
// `flat_hash_map`. However, if you need pointer stability and cannot store
// a `flat_hash_map` with `unique_ptr` elements, a `node_hash_map` may be a
// valid alternative. As well, if you are migrating your code from using
// `std::unordered_map`, a `node_hash_map` provides a more straightforward
// migration, because it guarantees pointer stability. Consider migrating to
// `node_hash_map` and perhaps converting to a more efficient `flat_hash_map`
// upon further review.

#ifndef ABEL_CONTAINER_NODE_HASH_MAP_H_
#define ABEL_CONTAINER_NODE_HASH_MAP_H_

#include <tuple>
#include <type_traits>
#include <utility>

#include "abel/algorithm/container.h"
#include "abel/container/internal/container_memory.h"
#include "abel/container/internal/hash_function_defaults.h"  // IWYU pragma: export
#include "abel/container/internal/node_hash_policy.h"
#include "abel/container/internal/raw_hash_map.h"  // IWYU pragma: export
#include "abel/memory/memory.h"

namespace abel {

namespace container_internal {
template<class Key, class Value>
class NodeHashMapPolicy;
}  // namespace container_internal

// -----------------------------------------------------------------------------
// abel::node_hash_map
// -----------------------------------------------------------------------------
//
// An `abel::node_hash_map<K, V>` is an unordered associative container which
// has been optimized for both speed and memory footprint in most common use
// cases. Its interface is similar to that of `std::unordered_map<K, V>` with
// the following notable differences:
//
// * Supports heterogeneous lookup, through `find()`, `operator[]()` and
//   `insert()`, provided that the map is provided a compatible heterogeneous
//   hashing function and equality operator.
// * Contains a `capacity()` member function indicating the number of element
//   slots (open, deleted, and empty) within the hash map.
// * Returns `void` from the `erase(iterator)` overload.
//
// By default, `node_hash_map` uses the `abel::hash` hashing framework.
// All fundamental and abel types that support the `abel::hash` framework have
// a compatible equality operator for comparing insertions into `node_hash_map`.
// If your type is not yet supported by the `abel::hash` framework, see
// abel/hash/hash.h for information on extending abel hashing to user-defined
// types.
//
// Example:
//
//   // Create a node hash map of three strings (that map to strings)
//   abel::node_hash_map<std::string, std::string> ducks =
//     {{"a", "huey"}, {"b", "dewey"}, {"c", "louie"}};
//
//  // Insert a new element into the node hash map
//  ducks.insert({"d", "donald"}};
//
//  // Force a rehash of the node hash map
//  ducks.rehash(0);
//
//  // Find the element with the key "b"
//  std::string search_key = "b";
//  auto result = ducks.find(search_key);
//  if (result != ducks.end()) {
//    std::cout << "Result: " << result->second << std::endl;
//  }
template<class Key, class Value,
        class Hash = abel::container_internal::hash_default_hash<Key>,
        class Eq = abel::container_internal::hash_default_eq<Key>,
        class Alloc = std::allocator<std::pair<const Key, Value>>>
class node_hash_map
        : public abel::container_internal::raw_hash_map<
                abel::container_internal::NodeHashMapPolicy<Key, Value>, Hash, Eq,
                Alloc> {
    using Base = typename node_hash_map::raw_hash_map;

  public:
    // Constructors and Assignment Operators
    //
    // A node_hash_map supports the same overload set as `std::unordered_map`
    // for construction and assignment:
    //
    // *  Default constructor
    //
    //    // No allocation for the table's elements is made.
    //    abel::node_hash_map<int, std::string> map1;
    //
    // * Initializer List constructor
    //
    //   abel::node_hash_map<int, std::string> map2 =
    //       {{1, "huey"}, {2, "dewey"}, {3, "louie"},};
    //
    // * Copy constructor
    //
    //   abel::node_hash_map<int, std::string> map3(map2);
    //
    // * Copy assignment operator
    //
    //  // Hash functor and Comparator are copied as well
    //  abel::node_hash_map<int, std::string> map4;
    //  map4 = map3;
    //
    // * Move constructor
    //
    //   // Move is guaranteed efficient
    //   abel::node_hash_map<int, std::string> map5(std::move(map4));
    //
    // * Move assignment operator
    //
    //   // May be efficient if allocators are compatible
    //   abel::node_hash_map<int, std::string> map6;
    //   map6 = std::move(map5);
    //
    // * Range constructor
    //
    //   std::vector<std::pair<int, std::string>> v = {{1, "a"}, {2, "b"}};
    //   abel::node_hash_map<int, std::string> map7(v.begin(), v.end());
    node_hash_map() {}

    using Base::Base;

    // node_hash_map::begin()
    //
    // Returns an iterator to the beginning of the `node_hash_map`.
    using Base::begin;

    // node_hash_map::cbegin()
    //
    // Returns a const iterator to the beginning of the `node_hash_map`.
    using Base::cbegin;

    // node_hash_map::cend()
    //
    // Returns a const iterator to the end of the `node_hash_map`.
    using Base::cend;

    // node_hash_map::end()
    //
    // Returns an iterator to the end of the `node_hash_map`.
    using Base::end;

    // node_hash_map::capacity()
    //
    // Returns the number of element slots (assigned, deleted, and empty)
    // available within the `node_hash_map`.
    //
    // NOTE: this member function is particular to `abel::node_hash_map` and is
    // not provided in the `std::unordered_map` API.
    using Base::capacity;

    // node_hash_map::empty()
    //
    // Returns whether or not the `node_hash_map` is empty.
    using Base::empty;

    // node_hash_map::max_size()
    //
    // Returns the largest theoretical possible number of elements within a
    // `node_hash_map` under current memory constraints. This value can be thought
    // of as the largest value of `std::distance(begin(), end())` for a
    // `node_hash_map<K, V>`.
    using Base::max_size;

    // node_hash_map::size()
    //
    // Returns the number of elements currently within the `node_hash_map`.
    using Base::size;

    // node_hash_map::clear()
    //
    // Removes all elements from the `node_hash_map`. Invalidates any references,
    // pointers, or iterators referring to contained elements.
    //
    // NOTE: this operation may shrink the underlying buffer. To avoid shrinking
    // the underlying buffer call `erase(begin(), end())`.
    using Base::clear;

    // node_hash_map::erase()
    //
    // Erases elements within the `node_hash_map`. Erasing does not trigger a
    // rehash. Overloads are listed below.
    //
    // void erase(const_iterator pos):
    //
    //   Erases the element at `position` of the `node_hash_map`, returning
    //   `void`.
    //
    //   NOTE: this return behavior is different than that of STL containers in
    //   general and `std::unordered_map` in particular.
    //
    // iterator erase(const_iterator first, const_iterator last):
    //
    //   Erases the elements in the open interval [`first`, `last`), returning an
    //   iterator pointing to `last`.
    //
    // size_type erase(const key_type& key):
    //
    //   Erases the element with the matching key, if it exists.
    using Base::erase;

    // node_hash_map::insert()
    //
    // Inserts an element of the specified value into the `node_hash_map`,
    // returning an iterator pointing to the newly inserted element, provided that
    // an element with the given key does not already exist. If rehashing occurs
    // due to the insertion, all iterators are invalidated. Overloads are listed
    // below.
    //
    // std::pair<iterator,bool> insert(const init_type& value):
    //
    //   Inserts a value into the `node_hash_map`. Returns a pair consisting of an
    //   iterator to the inserted element (or to the element that prevented the
    //   insertion) and a `bool` denoting whether the insertion took place.
    //
    // std::pair<iterator,bool> insert(T&& value):
    // std::pair<iterator,bool> insert(init_type&& value):
    //
    //   Inserts a moveable value into the `node_hash_map`. Returns a `std::pair`
    //   consisting of an iterator to the inserted element (or to the element that
    //   prevented the insertion) and a `bool` denoting whether the insertion took
    //   place.
    //
    // iterator insert(const_iterator hint, const init_type& value):
    // iterator insert(const_iterator hint, T&& value):
    // iterator insert(const_iterator hint, init_type&& value);
    //
    //   Inserts a value, using the position of `hint` as a non-binding suggestion
    //   for where to begin the insertion search. Returns an iterator to the
    //   inserted element, or to the existing element that prevented the
    //   insertion.
    //
    // void insert(InputIterator first, InputIterator last):
    //
    //   Inserts a range of values [`first`, `last`).
    //
    //   NOTE: Although the STL does not specify which element may be inserted if
    //   multiple keys compare equivalently, for `node_hash_map` we guarantee the
    //   first match is inserted.
    //
    // void insert(std::initializer_list<init_type> ilist):
    //
    //   Inserts the elements within the initializer list `ilist`.
    //
    //   NOTE: Although the STL does not specify which element may be inserted if
    //   multiple keys compare equivalently within the initializer list, for
    //   `node_hash_map` we guarantee the first match is inserted.
    using Base::insert;

    // node_hash_map::insert_or_assign()
    //
    // Inserts an element of the specified value into the `node_hash_map` provided
    // that a value with the given key does not already exist, or replaces it with
    // the element value if a key for that value already exists, returning an
    // iterator pointing to the newly inserted element. If rehashing occurs due to
    // the insertion, all iterators are invalidated. Overloads are listed
    // below.
    //
    // std::pair<iterator, bool> insert_or_assign(const init_type& k, T&& obj):
    // std::pair<iterator, bool> insert_or_assign(init_type&& k, T&& obj):
    //
    //   Inserts/Assigns (or moves) the element of the specified key into the
    //   `node_hash_map`.
    //
    // iterator insert_or_assign(const_iterator hint,
    //                           const init_type& k, T&& obj):
    // iterator insert_or_assign(const_iterator hint, init_type&& k, T&& obj):
    //
    //   Inserts/Assigns (or moves) the element of the specified key into the
    //   `node_hash_map` using the position of `hint` as a non-binding suggestion
    //   for where to begin the insertion search.
    using Base::insert_or_assign;

    // node_hash_map::emplace()
    //
    // Inserts an element of the specified value by constructing it in-place
    // within the `node_hash_map`, provided that no element with the given key
    // already exists.
    //
    // The element may be constructed even if there already is an element with the
    // key in the container, in which case the newly constructed element will be
    // destroyed immediately. Prefer `try_emplace()` unless your key is not
    // copyable or moveable.
    //
    // If rehashing occurs due to the insertion, all iterators are invalidated.
    using Base::emplace;

    // node_hash_map::emplace_hint()
    //
    // Inserts an element of the specified value by constructing it in-place
    // within the `node_hash_map`, using the position of `hint` as a non-binding
    // suggestion for where to begin the insertion search, and only inserts
    // provided that no element with the given key already exists.
    //
    // The element may be constructed even if there already is an element with the
    // key in the container, in which case the newly constructed element will be
    // destroyed immediately. Prefer `try_emplace()` unless your key is not
    // copyable or moveable.
    //
    // If rehashing occurs due to the insertion, all iterators are invalidated.
    using Base::emplace_hint;

    // node_hash_map::try_emplace()
    //
    // Inserts an element of the specified value by constructing it in-place
    // within the `node_hash_map`, provided that no element with the given key
    // already exists. Unlike `emplace()`, if an element with the given key
    // already exists, we guarantee that no element is constructed.
    //
    // If rehashing occurs due to the insertion, all iterators are invalidated.
    // Overloads are listed below.
    //
    //   std::pair<iterator, bool> try_emplace(const key_type& k, Args&&... args):
    //   std::pair<iterator, bool> try_emplace(key_type&& k, Args&&... args):
    //
    // Inserts (via copy or move) the element of the specified key into the
    // `node_hash_map`.
    //
    //   iterator try_emplace(const_iterator hint,
    //                        const init_type& k, Args&&... args):
    //   iterator try_emplace(const_iterator hint, init_type&& k, Args&&... args):
    //
    // Inserts (via copy or move) the element of the specified key into the
    // `node_hash_map` using the position of `hint` as a non-binding suggestion
    // for where to begin the insertion search.
    //
    // All `try_emplace()` overloads make the same guarantees regarding rvalue
    // arguments as `std::unordered_map::try_emplace()`, namely that these
    // functions will not move from rvalue arguments if insertions do not happen.
    using Base::try_emplace;

    // node_hash_map::extract()
    //
    // Extracts the indicated element, erasing it in the process, and returns it
    // as a C++17-compatible node handle. Overloads are listed below.
    //
    // node_type extract(const_iterator position):
    //
    //   Extracts the key,value pair of the element at the indicated position and
    //   returns a node handle owning that extracted data.
    //
    // node_type extract(const key_type& x):
    //
    //   Extracts the key,value pair of the element with a key matching the passed
    //   key value and returns a node handle owning that extracted data. If the
    //   `node_hash_map` does not contain an element with a matching key, this
    //   function returns an empty node handle.
    using Base::extract;

    // node_hash_map::merge()
    //
    // Extracts elements from a given `source` node hash map into this
    // `node_hash_map`. If the destination `node_hash_map` already contains an
    // element with an equivalent key, that element is not extracted.
    using Base::merge;

    // node_hash_map::swap(node_hash_map& other)
    //
    // Exchanges the contents of this `node_hash_map` with those of the `other`
    // node hash map, avoiding invocation of any move, copy, or swap operations on
    // individual elements.
    //
    // All iterators and references on the `node_hash_map` remain valid, excepting
    // for the past-the-end iterator, which is invalidated.
    //
    // `swap()` requires that the node hash map's hashing and key equivalence
    // functions be Swappable, and are exchaged using unqualified calls to
    // non-member `swap()`. If the map's allocator has
    // `std::allocator_traits<allocator_type>::propagate_on_container_swap::value`
    // set to `true`, the allocators are also exchanged using an unqualified call
    // to non-member `swap()`; otherwise, the allocators are not swapped.
    using Base::swap;

    // node_hash_map::rehash(count)
    //
    // Rehashes the `node_hash_map`, setting the number of slots to be at least
    // the passed value. If the new number of slots increases the load factor more
    // than the current maximum load factor
    // (`count` < `size()` / `max_load_factor()`), then the new number of slots
    // will be at least `size()` / `max_load_factor()`.
    //
    // To force a rehash, pass rehash(0).
    using Base::rehash;

    // node_hash_map::reserve(count)
    //
    // Sets the number of slots in the `node_hash_map` to the number needed to
    // accommodate at least `count` total elements without exceeding the current
    // maximum load factor, and may rehash the container if needed.
    using Base::reserve;

    // node_hash_map::at()
    //
    // Returns a reference to the mapped value of the element with key equivalent
    // to the passed key.
    using Base::at;

    // node_hash_map::contains()
    //
    // Determines whether an element with a key comparing equal to the given `key`
    // exists within the `node_hash_map`, returning `true` if so or `false`
    // otherwise.
    using Base::contains;

    // node_hash_map::count(const Key& key) const
    //
    // Returns the number of elements with a key comparing equal to the given
    // `key` within the `node_hash_map`. note that this function will return
    // either `1` or `0` since duplicate keys are not allowed within a
    // `node_hash_map`.
    using Base::count;

    // node_hash_map::equal_range()
    //
    // Returns a closed range [first, last], defined by a `std::pair` of two
    // iterators, containing all elements with the passed key in the
    // `node_hash_map`.
    using Base::equal_range;

    // node_hash_map::find()
    //
    // Finds an element with the passed `key` within the `node_hash_map`.
    using Base::find;

    // node_hash_map::operator[]()
    //
    // Returns a reference to the value mapped to the passed key within the
    // `node_hash_map`, performing an `insert()` if the key does not already
    // exist. If an insertion occurs and results in a rehashing of the container,
    // all iterators are invalidated. Otherwise iterators are not affected and
    // references are not invalidated. Overloads are listed below.
    //
    // T& operator[](const Key& key):
    //
    //   Inserts an init_type object constructed in-place if the element with the
    //   given key does not exist.
    //
    // T& operator[](Key&& key):
    //
    //   Inserts an init_type object constructed in-place provided that an element
    //   with the given key does not exist.
    using Base::operator[];

    // node_hash_map::bucket_count()
    //
    // Returns the number of "buckets" within the `node_hash_map`.
    using Base::bucket_count;

    // node_hash_map::load_factor()
    //
    // Returns the current load factor of the `node_hash_map` (the average number
    // of slots occupied with a value within the hash map).
    using Base::load_factor;

    // node_hash_map::max_load_factor()
    //
    // Manages the maximum load factor of the `node_hash_map`. Overloads are
    // listed below.
    //
    // float node_hash_map::max_load_factor()
    //
    //   Returns the current maximum load factor of the `node_hash_map`.
    //
    // void node_hash_map::max_load_factor(float ml)
    //
    //   Sets the maximum load factor of the `node_hash_map` to the passed value.
    //
    //   NOTE: This overload is provided only for API compatibility with the STL;
    //   `node_hash_map` will ignore any set load factor and manage its rehashing
    //   internally as an implementation detail.
    using Base::max_load_factor;

    // node_hash_map::get_allocator()
    //
    // Returns the allocator function associated with this `node_hash_map`.
    using Base::get_allocator;

    // node_hash_map::hash_function()
    //
    // Returns the hashing function used to hash the keys within this
    // `node_hash_map`.
    using Base::hash_function;

    // node_hash_map::key_eq()
    //
    // Returns the function used for comparing keys equality.
    using Base::key_eq;

    ABEL_DEPRECATED_MESSAGE("Call `hash_function()` instead.")
    typename Base::hasher hash_funct() { return this->hash_function(); }

    ABEL_DEPRECATED_MESSAGE("Call `rehash()` instead.")
    void resize(typename Base::size_type hint) { this->rehash(hint); }
};

// erase_if(node_hash_map<>, Pred)
//
// Erases all elements that satisfy the predicate `pred` from the container `c`.
template<typename K, typename V, typename H, typename E, typename A,
        typename Predicate>
void erase_if(node_hash_map<K, V, H, E, A> &c, Predicate pred) {
    container_internal::erase_if(pred, &c);
}

namespace container_internal {

template<class Key, class Value>
class NodeHashMapPolicy
        : public abel::container_internal::node_hash_policy<
                std::pair<const Key, Value> &, NodeHashMapPolicy<Key, Value>> {
    using value_type = std::pair<const Key, Value>;

  public:
    using key_type = Key;
    using mapped_type = Value;
    using init_type = std::pair</*non const*/ key_type, mapped_type>;

    template<class Allocator, class... Args>
    static value_type *new_element(Allocator *alloc, Args &&... args) {
        using PairAlloc = typename abel::allocator_traits<
                Allocator>::template rebind_alloc<value_type>;
        PairAlloc pair_alloc(*alloc);
        value_type *res =
                abel::allocator_traits<PairAlloc>::allocate(pair_alloc, 1);
        abel::allocator_traits<PairAlloc>::construct(pair_alloc, res,
                                                     std::forward<Args>(args)...);
        return res;
    }

    template<class Allocator>
    static void delete_element(Allocator *alloc, value_type *pair) {
        using PairAlloc = typename abel::allocator_traits<
                Allocator>::template rebind_alloc<value_type>;
        PairAlloc pair_alloc(*alloc);
        abel::allocator_traits<PairAlloc>::destroy(pair_alloc, pair);
        abel::allocator_traits<PairAlloc>::deallocate(pair_alloc, pair, 1);
    }

    template<class F, class... Args>
    static decltype(abel::container_internal::DecomposePair(
            std::declval<F>(), std::declval<Args>()...))
    apply(F &&f, Args &&... args) {
        return abel::container_internal::DecomposePair(std::forward<F>(f),
                                                       std::forward<Args>(args)...);
    }

    static size_t element_space_used(const value_type *) {
        return sizeof(value_type);
    }

    static Value &value(value_type *elem) { return elem->second; }

    static const Value &value(const value_type *elem) { return elem->second; }
};
}  // namespace container_internal

namespace container_algorithm_internal {

// Specialization of trait in abel/algorithm/container.h
template<class Key, class T, class Hash, class KeyEqual, class Allocator>
struct is_unordered_container<
        abel::node_hash_map<Key, T, Hash, KeyEqual, Allocator>> : std::true_type {
};

}  // namespace container_algorithm_internal


}  // namespace abel

#endif  // ABEL_CONTAINER_NODE_HASH_MAP_H_
